tailieunhanh - Fundamentals of Engineering Electromagnetics - Chapter 2

Tĩnh điện hạn mang lại tầm nhìn của Benjamin Franklin, diều "và phím" thử nghiệm, bình Leyden, lông mèo, và các thanh thủy tinh. Những điều này và tương tự như thí nghiệm đã báo trước sự phát hiện của lực điện từ và nằm trong số những người đầu tiên ghi lại trong thời đại công nghiệp. Các lực lượng do tĩnh điện đã được biết đến từ thời gian của người Hy Lạp cổ đại, nhưng kỷ luật tiếp tục là trọng tâm của nhiều nghiên cứu và phát triển. Hầu hết các quá trình điện rơi vào. | 2 Applied Electrostatics Mark N. Horenstein Boston University Boston Massachusetts . INTRODUCTION The term electrostatics brings visions of Benjamin Franklin the kite and key experiment Leyden jars cat fur and glass rods. These and similar experiments heralded the discovery of electromagnetism and were among some of the first recorded in the industrial age. The forces attributable to electrostatic charge have been known since the time of the ancient Greeks yet the discipline continues to be the focus of much research and development. Most electrostatic processes fall into one of two categories. Sometimes electrostatic charge produces a desired outcome such as motion adhesion or energy dissipation. Electrostatic forces enable such diverse processes as laser printing electrophotography electrostatic paint spraying powder coating environmentally friendly pesticide application drug delivery food production and electrostatic precipitation. Electrostatics is critical to the operation of micro-electromechanical systems MEMS including numerous microsensors transducers accelerometers and the microfluidic lab on a chip. These microdevices have opened up new vistas of discovery and have changed the way electronic circuits interface with the mechanical world. Electrostatic forces on a molecular scale lie at the core of nanodevices and the inner workings of a cell s nucleus are also governed by electrostatics. A myriad of selfassembling nanodevices involving coulombic attraction and repulsion comprise yet another technology in which electrostatics plays an important role. Despite its many useful applications electrostatic charge is often a nuisance to be avoided. For example sparks of electrostatic origin trigger countless accidental explosions every year and lead to loss of life and property. Less dramatically static sparks can damage manufactured products such as electronic circuits photographic film and thin-coated materials. The transient voltage and current of a single